Due to the improved fit and fluid sealing properties provided by leg elasticization, manufacturers of disposable diapers have, in recent years, developed various methods and apparatus for attaching elastic strips to the leg areas of the diapers. Because of the high speed, continuous nature of diaper manufacturing methods, virtually all of the commercially practicable processes have utilized a continuous elastic ribbon affixed to the diaper in the leg areas and subsequently cut either prior to or as a part of the severing of the continuous web into separate diapers. Typical of these processes and apparatus is that disclosed in U.S. Pat. No. 4,081,301 to Buell. This patent discloses adhering of the continuous elastic ribbon only in discrete, intermittent areas corresponding to the leg areas in a finished diaper. After adhering of the ribbon to a continuous web, the ribbon and the web are simultaneously cut at what will be the waist of the diaper when the manufacturing process is finished. The drawback of this process is that it is inefficient from the material use aspect in that it leaves an unneeded length of elastic attached to the diaper. Another approach to handling the problem is disclosed in U.S. Pat. No. 4,227,952 to Sabee. In the method of this patent, the elastic ribbon is continuously applied to the web, however, before the attachment of the ribbon to the web, the latter is tucked in the areas of the web corresponding to the waist areas of the finished diapers. Consequently, the elastic ribbon is attached to the web only in the leg areas of the finished diaper. The elastic ribbon is then severed at the points opposite the tucked areas of the web and the web is then untucked so that elastic is only in the leg areas of the finished diaper and the waist areas contain no unneeded elastic. The problem with this method and the apparatus used in it is that it is difficult to operate at the high speeds required for commercial usefulness. Much of the difficulty of the Sabee approach is due to the attempt to intermesh, in gear wheel fashion, projecting tucking members with members defining receptacles to form tucks in the web. Intermeshing of these members in this manner is too abrupt and presents positioning difficulties which prevent high speed operation and places too much stress on the web. Also, the depth of the tuck is limited by the width of the receptacles openings through which the tucking members must rotate to form the tucks.
A second approach using a tucking method is that disclosed in U.S. application Ser. No. 181,821, filed Aug. 27, 1980, now abandoned. The apparatus and method of this application solves the intermeshing difficulties of Sabee by mounting the projecting tucking members on a conveyor chain in a manner such that they are moveable relative to the conveyor chain in the direction of their length. The movement of the tucker members into the tuck defining receptacles is caused by cam means connected to the tucker members so that the rate of insertion of the tucker members into receptacles and the position at which they are inserted is controlled relatively independently of the position and movement of the conveyor chain carrying the tucker members. However, this approach has the problems of considerable complexity resulting in high initial cost of the apparatus and substantial wear requiring constant maintenance and adding further to the overall cost.
It is a principal object of this invention to provide, for use in a high speed production process and apparatus, a relatively simple, efficient method and apparatus for attaching a continuously moving elastic ribbon to a continuously moving web such that only selected discrete areas of a finished conformable garment fabricated from the web will be elasticized. The conformable garment may be a disposable diaper in which only the areas of the web corresponding to the leg areas in finished diapers will be elasticized. It is a particular object of this invention to provide a method and apparatus for forming tucks in a continuously moving web utilizing a relatively simple apparatus and method which facilitates and positions the forming of the tucks to permit their forming at high speed.
The objectives of the invention are accomplished by providing a first continuously moving conveyor means having a supporting surface with spaced apart gaps therein on to which a web is continuously moved and a second continuously moving conveyor means carrying a plurality of tucker bars rigidly mounted on and extending from the second conveyor means and inserted into and removed from the gaps of the first conveyor means as the two conveyor means move opposite each other in the same direction. The first conveyor means includes a pair of endless conveyor chains having a plurality of groups of spaced apart pairs of rollers with the rollers of each pair spaced apart to define the aforementioned gaps. A plurality of bars are disposed between each pair of rollers and form said supporting surface. The first and second conveyor means are moved along paths such that, during a portion of their movement along the paths, each tucker bar extending from the second conveyor means is in registry with the gaps of the first conveyor means. While the tucker bars are in registry with the gaps and the two conveyor means are moving in the same direction, the first conveyor means is directed, at the feed end of the apparatus, toward the second conveyor means and the tucker bars at a relatively gradual rate by a guide means such that the tucker bars are inserted into the gaps to form tucks in the web. During the insertion movement the tucker bars are rigidly carried by the second conveyor means at a substantially constant angle such that the insertion of the tucker bars into the gaps and the extent of this insertion is due largely to the movement of the two conveyor means toward each other rather than the rotation of the tucker bars or their movement relative to the second conveyor means.
After the tucker bars are inserted to the maximum depth in the gaps to complete the tucks, the elastic ribbons are brought into contact with the web so that the elastic spans the tucks and engages only the areas of the web between the tucks. The elastic ribbons are then cut opposite the tucks and the first conveyor means is guided away from the second conveyor means so that the tucker bars are withdrawn from the gaps. As the web leaves the apparatus at its exit end, the speed of movement of the web is increased to remove the tucks.